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URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11800
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Item Síntese de novos herbicidas derivados do 1, 2a, 4a, 5- tetrametil- 8- oxabiciclo[ 3. 2. 1] oct- 6- en- 3- ona(Química Nova, 2004-03) Barbosa, Luiz Cláudio de Almeida; Maltha, Célia Regina Álvares; Demuner, Antônio Jacinto; Filomeno, Claudinei Andrade; Silva, Antônio Alberto daIn this paper we report the synthesis of biologically active compounds through a [3+4] cycloaddition reaction to produce the main frame structure, followed by several conventional transformations. The 1,2a,4a,5-tetramethyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (11) obtained from a [3+4] cycloaddition reaction was converted into 1,2a,4a,5-tetramethyl-6,7-exo-isopropylidenedioxi-8 -oxabicyclo[3.2.1]octan-3-one (13) in 46% yield. This was further converted into the alcohols 1,2a,4a,5-tetramethyl-6,7-exo-isopropylidenedioxi-8-oxabicyclo[3.2.1]octan-3 a-ol (14), 1,2a,4a,5-tetramethyl-6,7-exo-isopropylidenedioxi-8 -oxabicyclo[3.2.1]octan-3b-ol (15), 1,2a,4a,5-tetramethyl-3-butyl-6,7-exo-isopropylidenedioxi-8-oxabicyclo[3.2.1]octan-3 a-ol (17), 1,2a,4a,5-tetramethyl-3-hexyl-6,7-exo-isopropylidenedioxi-8-oxabicyclo[3.2.1]octan-3 a-ol (18) and 1,2a,4a,5-tetramethyl-3-decyl-6,7-exo-isopropylidenedioxi-8-oxabicyclo[3.2.1]octan-3 a-ol (19). Dehydration of 17, 18 and 19 with thionyl chloride in pyridine resulted in the alkenes 20, 21 and 22 in ca. 82% - 89% yields from starting alcohols. The herbicidal activity of the compounds synthesized was evaluated at a concentration of 100 µg g-1. The most active compound was 21 causing 42,7% inhibition against Cucumis sativus L.Item Seasonal variation in the composition of volatile oils from Schinus terebinthifolius raddi(Química Nova, 2007) Barbosa, Luiz Cláudio Almeida; Demuner, Antônio Jacinto; Clemente, Alan Dumont; Paula, Vanderlúcia Fonseca de; Ismail, Faiz M. D.Essential oils from leaves, ripe and unripe fruits of Schinus terebinthifolius growing in Brazil were investigated. Oil content from either ripe or unripe fruits was similar (4.65% and 3.98%, respectively). Sesquiterpenes (from 78.0% to 90.4%) dominated the oil content of both leaves and unripe fruit. The essential oils were tested in vitro for their allelopathic activity on germination and radicle growth of Lactuca sativa and Cucumis sativus at 1,000 and 10,000 µg mL-1concentrations. The three samples tested were more active in inhibiting the radicle growth for L. sativa (88.6-92.4%) than for C. sativus (50.5-84.5%) at 10,000 µg mL-1 concentration.Item Síntese e avaliação da atividade fitotóxica de novos análogos oxigenados do ácido helmintospórico(Química Nova, 2003-09) Barbosa, Luiz Cláudio de Almeida; Demuner, Antônio Jacinto; Maltha, Célia Regina Álvares; Silva, Patrícia Silvana da; Silva, Antônio Alberto daSeveral compounds related to helminthosporic acid (3) were synthesized via the [3+4] cycloaddition. The reaction of 3-hydroxymethyl-2-methylfuran (12) with 1,1,3,3-tetrabromo-4-methylpentan-2-one (13) resulted in 7-hydroxymethyl-4a-isopropyl-1a-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (8) (37%) and 7-hydroxymethyl-2a-isopropyl-1a-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (14) (12%), which were converted into 7-formyl-4a-isopropyl-1a-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (16) (32% from 8) and 7-formyl-2a-isopropyl-1a-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (18) (40% from 14), respectively. Reduction of (8) resulted in 7-hydroxymethyl-4a-isopropyl-1a-methyl-8-oxabicyclo[3.2.1]oct-6 -en-3a-ol (11) (63% from 8) and 7-hydroxymethyl-4a-isopropyl-1a-methyl-8-oxabicyclo[3.2.1]oct-6-en-3 b-ol (15) (30% from 8). The 4a-isopropyl-1a-methyl-3-oxo-8-oxabicyclo[3.2.1]oct-6-en-7-oic acid (19) was obtained by oxidation of (16) (78%). The results of biological tests are described in details. The best result was observed for compound (15) that caused 76% inhibition on the root growth of D. tortuosum.Item Chemical constituents of the bark of Gallesia gorazema(Fitoterapia, 1999-04-01) Barbosa, Luiz CLaudio Almeida; Demuner, Antônio Jacinto; Teixeira, Robson; Madruga, M. S.Chemical composition analysis of the essential oil from the bark of Gallesia gorazema was carried out by GC/MS. This analysis led to the identification of six non-sulfurated and 19 sulfurated compounds.Item Phytotoxic effectes of metabolites from Alternaria euphorbiicola against its host plant Euphorbia heterophylla(Química Nova, 2013-05-24) Varejão, Eduardo Vinícius Vieira; Demuner, Antônio Jacinto; Barbosa, Luiz Cláudio de Almeida; Barreto, Robert WeingartA bioassay-guided fractionation of culture filtrates of the fungus Alternaria euphorbiicola, a pathogen of the weed Euphorbia heterophylla, led to the isolation of anhydromevalonolactone (1), tyrosol (2), (R)-( - )-mevalonolactone (3), and cycloglycylproline (4). When tested on the punctured leaves of the host plant, these compounds produced bleached lesions with dark brown margins at concentrations as low as 80 µM. When tested on the leaves of other relevant weeds, only cycloglycylproline showed selective activity against E. heterophylla. This is the first report on the isolation of phytotoxins from A. euphorbiicola and on the phytotoxicity of anhydromevalonolactone, (R)-( - )-mevalonolactone, and cycloglycylproline.Item Synthesis of new phytogrowth-inhibitory substituted Aryl-p-Benzoquinones(Chemistry & Biodiversity, 2006-05-23) Barbosa, Luiz Cláudio de Almeida; Alvarenga, Elson Santiago de; Demuner, Antônio Jacinto; Virtuoso, Luciano Sindra; Silva, Antônio AlbertoReaction of [(2-alkyloxy)methyl]-1,4-dimethoxybenzene 10 (alkyl=butyl, hexyl, decyl, tridecyl, tetradecyl, hexadecyl, and octadecyl) with ceric ammonium nitrate in order to produce p-benzoquinones (=cyclohexa-2,5-diene-1,4-diones) afforded 5-[(alkyloxy)methyl]-2-(4-formyl-2,5-dimethoxyphenyl)benzo-1,4-quinones 12a-12g in yields that varied from 46 to 97%, accompanied by 2-[(alkyloxy)methyl]benzo-1,4-quinones 11a-11g in only small quantities (< or =5%). These quinones resemble the natural phytotoxic compound sorgoleone, found in Sorghum bicolor. This reaction exemplifies a general procedure for the synthesis of novel aryl-substituted p-benzoquinones. The selective effects of compounds 12a-12g, at the concentration of 5.5 ppm, on the growth of Cucumis sativus, Sorghum bicolor, Euphorbia heterophylla, and Ipomoea grandifolia were evaluated. All compounds caused some inhibition upon the aerial parts and root growth of the tested plants. The most active compound, 2-(4-formyl-2,5-dimethoxyphenyl)-5-[(tridecyloxy)methyl]-benzo-1,4-quinone (12d), caused between 3 and 18%, and 12 and 29% inhibition on the roots and aerial parts development of Cucumis sativus and Sorghum bicolor, respectively, and between 77 and 85%, and 34 and 52% inhibition on the roots and aerial parts growth of Euphorbia heterophylla and Ipomoea grandifolia, respectively.